1. Field of the Invention
The subject invention is directed to an intravenous lead, and more particularly, to an implantable cardiac lead and having mapping capabilities to facilitate safe placement of the lead within the coronary sinus.
2. Background of the Related Art
Electrical therapeutic and diagnostic devices for the heart, such as pacemakers and defibrillators, commonly employ leads for connecting an electrical pulse generator to excitable cardiac tissue, usually within the right ventricle and/or right atrium. Pacing and defibrillation leads commonly include one or more distal electrodes and often have outwardly projecting tines near the distal tip or an active fixation screw to hold the electrode in contact with endocardial tissue in the right ventricle or atrium.
It has been found that cardiac stimulation can have a beneficial effect in treating congestive heart failure. However, pacing therapy for treating congestive heart failure often requires left ventricular stimulation, either alone or in conjunction with right ventricular stimulation and defibrillation. Left ventricular pacing presently requires placement of an epicardial lead by way of a thoracotomy, which is a high risk procedure performed under general anesthesia. To obviate the need for a thoracotomy, left ventricular access leads have been developed which are introduced through the coronary sinus and then advanced through the coronary veins so that the distal electrode of lead can be positioned on the surface of the left ventricle near the apex of the heart.
The coronary veins of the heart are of a relatively small diameter. The lead extended therethrough must therefore, be of a relatively small diameter, as compared to leads used for right ventricular stimulation. Cardiac and respiratory motion as well as blood flow can cause a lead to become dislodged. Accordingly, the lead must include structure to anchor the electrode at a desired location.
It would be beneficial to provide a left ventricular pacing lead configured for advancement through the coronary sinus and into the coronary vein, which has structure for anchoring the distal end of the lead at a desired site of stimulation, and which could be used in certain instances for defibrillation.
The subject invention is directed to a new and useful implantable cardiac lead adapted and configured for advancement through the coronary sinus and into the coronary vein that includes cooperating first (outer) and second (inner) elongated lead bodies. The first lead body has opposed proximal and distal end portions, an interior lumen extending therethrough, at least one distal electrode operatively associated with the distal end portion thereof and a proximal electrode operatively associated with the proximal end thereof. Preferably, the first lead body includes sensor means that are operatively associated with the distal end portion thereof for measuring blood flow parameters to facilitate placement of the distal end portion of the first lead body adjacent the coronary sinus, and seal means for sealing the interior lumen of the first lead body during insertion of the first lead body through the coronary venous system.
The second (inner) lead body has opposed proximal and distal end portions, at least one distal electrode operatively associated with the distal end portion thereof, a proximal electrode operatively associated with the proximal end thereof, and it is dimensioned and configured for accommodation within the interior lumen of the first (outer) lead body. Preferably, the proximal end portion of the first lead body and the proximal end portion of the second lead body include means for connecting the first lead body to the second lead body.
In accordance with the subject invention, the second lead body has a length that is greater than the length of the first lead body. Preferably, the length of the first lead body is about between 50 and 80 cm, and the length of the second lead body is about between 60 and 100 cm. preferably, the outer diameter of the first lead body is about between 6 and 9 F, and the outer diameter of the second lead body is about between 3 and 5 F.
A conductor extends through the first lead body to connect the distal electrode and the proximal electrode, and a conductor extends through the second lead body to connect the distal electrode and the proximal electrode. Additionally, the second lead body has an interior lumen extending therethrough to accommodate a stylet. In one embodiment of the invention, the distal electrode of the first lead body is a ring electrode spaced from the distal end of the lead body for pacing and/or sensing. Alternatively, the distal electrode of the first lead body is a coil electrode used for defibrillation, or as a ground electrode. In one embodiment of the invention, the distal electrode of the second lead body is a ring electrode that is spaced from the distal end of the second lead body for pacing and/or sensing. Alternatively, the distal electrode of the second lead body is configured as tip electrode for pacing and/or sensing. The proximal electrode of the second lead body is preferably defined as a pin connector.
The second or inner lead body preferably has fixation means operatively associated with the distal end portion thereof for anchoring the lead within the coronary venous system. In addition, the first or outer lead body may have fixation means operatively associated with the distal end portion thereof. In either case, the fixation means may be defined by at least one radially expandable tine, by an expandable stent configured for movement between a retracted position and an expanded position, or by a plurality of radially expandable arms configured for movement between a retracted position and an extended position. Furthermore, the fixation means may have a coating containing a medicament such as a steroid.
The subject invention is also directed to a new and useful method of implanting a cardiac lead comprising the steps of passing an elongated outer lead body having an interior lumen through the venous system to a selected coronary vein, and extending an elongated inner lead body into the interior lumen of the outer lead body so that a distal end portion of the inner lead body extends from a distal end portion of the outer lead body.
The method further includes that steps of securing the inner and outer lead bodies to one another, and anchoring at least one of the distal end portion of the inner lead body and the distal end portion of the outer lead body within the selected coronary vein. The step of anchoring at least one of the distal end portion of the inner lead body and the distal end portion of the outer lead body within the selected coronary vein includes deploying an expandable stent operatively associated with at least one of the distal end portion of the inner lead body and the distal end portion of the outer lead body, or deploying expandable arms operatively associated with at least one of the distal end portion of the inner lead body and the distal end portion of the outer lead body.
These and other aspects of the subject invention and the method of using the same will become more readily apparent to those having ordinary skill in the art from the following detailed description of the invention taken in conjunction with the drawings described hereinbelow.